J. J. Hunter

The effect of partial defoliation, leaf position and developmental stage of the vine on the photosynthetic activity of vitis vinifera L. cv cabernet sauvignon

The effect of partial defoliation, :eaf position and developmental stage of the vine on the photosynthesis, stomatal resistance and transpiration of Vitis vinifera L. cv Cabernet Sauvignon was investigated. Partially defoliated vines displayed a higher rate of photosynthesis, generally increasing with degree of defoliation. The highest photosynthetic rates were found for the apical leaves, while those of the leaves opposite and below the bunches were restricted. Generally, rate of photosynthesis declined as the season progressed. The course of transpiration rate and stomata! resistance correlated with that of the rate of photosynthesis. However, transpiration and photosynthesis correlated poorly in the case of the apical leaves. In general, photon flux density and relative humidity at the leaf surface increased with an increase in defoliation percentage for all leaf positions. Leaf temperature was not significantly affected by partial defoliation. The results of the investigation suggested that excess vegetative growth is detrimental to interior-canopy microclimate as well as the photosynthetic rate of the entire vine. Partial defoliation seemed to provide a means to reduce some of the deleterious effects of vigorous growth.

Invertase activity, grape berry development and cell compartmentation

Abstract The effect of gibberellic acid on grape ( Vitis vinifera L., ev. Sultanina) growth, β-fructofuranosidase (EC 3.2.1.26) activity and carbohydrate levels was investigated throughout berry development and ripening. Although the fruits responded to hormone application with the expected increase in size, growth was not correlated with enzymic activity and hexose accumulation. This suggests that there is no direct regulatory relationship between invertase and the rate of assimilate import. However, fructose:glucose ratios changed from 0.1 in green berries to 1.0 in mature samples. The latter situation can be reconciled with the 1:1 stoichiometry of sucrolysis by invertase. It is suggested that this is attributable to a spatial separation of substrate and enzyme in green tissue. Compartmentation studies indicate that mesocarp cell integrity gradually deteriorates during ripening, which allows invertase to leak out of the vacuole into the surrounding tissue. In fact, the protein fraction retrieved from a buffered medium after incubation of ripening berry slices contained a soluble invertase of presumably vacuolar origin with an acid pH-activity profile and a pI of about 4.

The Effect of Partial Defoliation on Growth Characteristics of Vitis vinifera L. cv. Cabernet Sauvignon I. Vegetative Growth

The effect of partial defoliation over the whole canopy on the reproductive growth of Vitis vinifera L. cv. Cabernet Sauvignon was investigated. The 33% defoliation treatment prior to pea size and the 66% defoliation treatment prior to veraison adversely affected fresh mass per berry and yield at harvest. The 33% defoliation treatment from veraison increased fresh berry mass. Partial defoliation had no effect on berry water content. Dry matter started to accumulate rapidly only from after pea size stage. The fresh berry mass:cane mass ratio increased with partial defoliation from veraison. Leaf area/g fresh mass results indicated that control vines carried excess foliage which prevented maximum photosynthetic activity. Partial defoliation of the canopy improved budding percentage, generally increasing with increasing defoliation, whereas bud fertility was improved only by 33% defoliation. In general, leaf removal from bud break and berry set was more effective in improving budding, whereas bud fertility was favoured by partial defoliation from bud break.

The effect of partial defoliation, leaf position and developmental stage of the vine on leaf chlorophyll concentration in relation to the photosynthetic activity and light intensity in the canopy of Vitis vinifera L. cv. Cabernet Sauvignon

The effect of partial defoliation and leaf position on leaf chlorophyll concentration in relation to the photosynthetic activity and light intensity in the canopy of Vitis vinifera L. cv. Cabernet Sauvignon was investigated at berry set, pea size, veraison and ripeness stages. The leaves of the severely defoliated vines appeared to contain the highest chlorophyll concentration. In general, chlorophyll a decreased as the leaves were situated progressively deeper into the canopy. No consistent relationship between chlorophyll concentration, light intensity and photosynthetic activity could be found for the different leaf positions. However, to obtain leaves that photosynthesize optimally, the amount and time of leaf removal in the grapevine canopy must be carefully planned.

Distribution of 14C-Photosynthetate in the Shoot of Vitis vinifera L. cv Cabernet Sauvignon II. The Effect of Partial Defoliation

The effect of partial defoliation of Vitis vinifera L. cv Cabernet Sauvignon on the distribution of photosynthetates, originating in leaves in different positions on the shoot at berry set, pea size, veraison and ripeness stages, was investigated. Partial defoliation (33% and 66%) resulted in a higher apparent photosynthetic effectivity for all the remaining leaves on the shoot. The pattern of distribution of photosynthetates would seem to stay the same between the defoliation treatments. The control vines were found to carry excess foliage. Optimal photosynthetic activity of all the leaves on the vine was therefore not reached.

The Effect of Partial Defoliation on Quality Characteristics of Vitis vinifera L. cv. Cabernet Sauvignon Grapes 1. Sugars, Acids and pH

The effect was studied of partial defoliation (33% and 66%) on the sugar and acid accumulation and pH in grapes of Vitis vinifera L. cv. Cabernet Sauvignon. Although the total soluble sugar (TSS) in grapes of partially defoliated vines was significantly higher than that of non-defoliated vines in some cases, no significant differences were generally found. No significant differences in total titratable acidity (TT A) were found between treatments. The timing of defoliation had no effect on TSS in grapes, whereas TT A tended to be higher the earlier partial defoliation was commenced. In general, 33 % and 66% defoliated vines respectively produced approximately 33 % and 200% more TSS and TT A in the fruit per cm2 leaf area than non-defoliated vines. No significant differences between defoliation treatments were found on a per gram dry berry mass or per berry basis for glucose and fructose or tartaric and malic acid. However, 66% defoliated vines had significantly less soluble solids in berries per shoot, which was probably caused by a lower total berry mass per shoot. Although no significant differences in sugar composition could be found between defoliation treatments, tartaric acid levels tended to be higher and malic acid levels lower as a result of partial defoliation. Partial defoliation had no effect on the accumulation patterns of sugars and acids. Glucose dominated in berries at veraison, with fructose dominating at ripeness. The highest total tartaric and malic acid concentrations occurred at pea size. Malic acid content decreased rapidly from veraison, whereas the decrease in tartaric acid was not pronounced. Must pH was not affected by partial defoliation. The results seem to suggest that the general metabolism of vines was favourably changed by partial defoliation, mainly in terms of a more favourable source: sink ratio, more efficient photosynthesis, and an improved canopy microclimate.

Anthocyanin yield and skin softening during maceration, as affected by vineyard row orientation and grape ripeness of Vitis vinifera L. cv. Shiraz.

Anthocyanin and mechanical properties were evaluated on Shiraz grapes, picked from both sides of North-South and East-West vineyard row orientations at two harvest dates. Wines were made from each combination. The evaluation and evolution of crushed skin mechanical properties during maceration-fermentation, as also affected by grape ripeness, are shown for the first time. No significant differences in anthocyanin content were found in the grapes between the two vineyard row orientations. However, a significant decrease in anthocyanins and berry skin break force (also referred as skin hardness or strength) was found between the two harvest dates. During maceration, a reduction in the crushed berry skin break force of more than 15% occurred. The intact berries and macerated skins showed similarity in skin break energy values. The anthocyanin profile of the grapes and of the wines prominently displayed malvidin forms, changed mainly by the ripeness level of the grapes.

Effect of Seasonal Canopy Management on the Performance of Chenin blanc/99 Richter Grapevines

The effect of seasonal canopy management on the performance of a Chenin blanc/99Richter vineyard with excessive vegetative growth and trained onto a Lengthened Perold trellising system, was studied. No canopy management (shoots growing in all directions) resulted in over-exposure of the bunch zone directly above the cordon, whereas sunlight reflection from the soil was drastically reduced. In contrast, canopy management led to a much more balanced penetration of sunlight into the bunch zone - here, shoot positioning played a big role. Air flow through the canopy was highest when partial defoliation, in combination with suckering and shoot positioning, was applied; these practices had the highest impact on canopy microclimate and appearance. Canopy management reduced the incidence and severity of Botrytis/sour rot - shoot positioning in particular seemed critical. Highest yields were obtained by applying shoot positioning and defoliation or topping. Although suckering was labour intensive and reduced yields, it resulted in significant labour savings for critical time-dependent actions such as pruning and harvesting. Total grape quality and wine typical flavour were improved by seasonal canopy management.

Berry Characterisation of cv Shiraz According to Position on the Rachis

In this study, characterisation of the physical and compositional parameters of berries located in different positions on the rachis of Shiraz/R99 bunches was done. Berries were divided according to position on the rachis (apical, median and basal) and berry weight, resulting in four berry weight classes, averaging 0.86 g, 1.29 g, 1.74 g and 2.26 g and 0.74, 1.18, 1.59 and 2.09 cm3, respectively. The berries were analysed individually. The fresh weight of the berries comprised approximately 4% seeds, 20% skin and 76% flesh. Different percentage distributions were found for each class of berry weight and according to position on the rachis. From the top to the bottom rachis position, an increase in skin proportion value and a decrease in flesh and seed proportion value occurred. Skins decreased and flesh increased in proportion from the smallest to the largest berry size. The seed maintained a relatively stable proportion, irrespective of berry size. Larger berries had more flesh compared to skin than smaller berries. A higher level of soluble solids occurred in the shoulder to middle bunch area (28.7 °B and 28.6 °B, respectively) than in the bottom area (27.6 °B). It is extremely difficult to obtain uniform berry size and composition under field conditions. Continuous efforts are required to reduce variation and the potential negative impact on wine quality and consistency of wine style.

Integrative Effects of Vine Water Relations and Grape Ripeness Level of Vitis vinifera L. cv. Shiraz/Richter 99. I. Physiological Changes and Vegetative-Reproductive Growth Balances

The water relations and physiological status of the grapevine are critical for obtaining a quality product and for fully exploring vineyard and grape potential. The objective of this investigation was to determine the effect of grapevine water status (induced by means of two field water capacity-based irrigation levels, 75% and 100%, applied at single and combined vine developmental stages) on morphological and physiological changes in Vitis vinifera L. cv. Shiraz/Richter 99 grapevines and grapes (harvested at different soluble solid levels) under field conditions. The integrative effects of vine water relations and grape ripeness level, specifically in a Mediterranean high winter rainfall area, have not yet been investigated systematically. The terroir affected the reaction of the vines to treatments. The soil displayed high water-holding capacity and a buffer against favourable evapotranspiration conditions, even with a western aspect and being subjected to long and relatively dry seasons, with frequent occurrence of high temperatures and grapevines with fully developed canopies. The vines did not seem overly stressed – in line with the relatively high base soil water fractions of mostly more than 50% of field water capacity. Primary and secondary leaf water potential and stem water potential displayed similar patterns and the water potential of the primary and secondary leaves was similar. Despite relatively high base soil water contents that prevented excessively low plant water potential and classic leaf and berry behaviour to surface, the vines still responded in a noticeable way to volume and timing of irrigation in relation to the grape ripeness level status. Water relations, ripeness level and terroir conditions showed an integrated, steering impact on physiological, vegetative and reproductive behaviour. Post-veraison irrigated vines were expected to maintain relatively high water potential during the last weeks of the ripening period, but this seemed not to be the case. All vines seemed to have recuperated/stabilised during this time, maintaining their water balances. Physical, physiological and compositional changes in the berry during late ripening under field conditions were clarified further. New information was obtained on the relationships between the behaviour of the root system, canopy and grapes and the changing terroir conditions during the ripening period.